如何通过组合两个列表中的项目来创建字典？

Question

key_list=['number','alpha']
value_list=[['1','a'],['2','b']]

I want to collect elements in this pattern:

dict = {}
dict.setdefault(key_list[0],[]).append(value_list[0][0])
dict.setdefault(key_list[0],[]).append(value_list[1][0])
dict.setdefault(key_list[1],[]).append(value_list[0][1])
dict.setdefault(key_list[1],[]).append(value_list[1][1])

How to do this in loop?

Answer 1

You can simply zip the values of the values_list and then zip the result with the key_list , with dictionary comprehension, like this

>>> {k: v for k, v in zip(key_list, zip(*value_list))}
{'alpha': ('a', 'b'), 'number': ('1', '2')}

---

You can understand this, step-by-step, like this

>>> list(zip(*value_list))
[('1', '2'), ('a', 'b')]

Now, zip ping this with key_list will give us

>>> list(zip(key_list, zip(*value_list)))
[('number', ('1', '2')), ('alpha', ('a', 'b'))]

Now, you can either use dict function to create the dictionary, like shown by mhawke,

>>> dict(zip(key_list, zip(*value_list)))
{'alpha': ('a', 'b'), 'number': ('1', '2')}

or use the dictionary comprehension, as I have shown above.

Answer 2

zip() comes in very handy for this sort of thing:

key_list=['number','alpha']
value_list=[['1','a'],['2','b']]
d = dict(zip(key_list, zip(*value_list)))
print(d)

Output

{'alpha': ('a', 'b'), 'number': ('1', '2')}

Basically this works by unpacking values_list so that the individual items (themselves lists) are passed as arguments to the zip() builtin function. This has the affect of collecting the numbers and alphas together. That new list is then zipped with key_list to produce another list. Finally a dictionary is created by calling dict() on the zipped list.

Note that this code does rely on the order of elements in value_list . It assumes that the numeric value always precedes the alpha value. It also produces a dictionary of tuples not lists . If that is a requirement then using a dict comprehension (as per thefourtheye's answer) allows you to convert the tuples to lists as the dictionary is built:

key_list=['number','alpha']
value_list=[['1','a'],['2','b']]
d = {k: list(v) for k, v in zip(key_list, zip(*value_list))}
>>> print(d)
{'alpha': ['a', 'b'], 'number': ['1', '2']}